1. Field of the Invention
The invention relates generally to watercraft, specifically to watercraft hulls and more specifically to flat bottom watercraft hulls.
2. Background of the Invention
Conventional recreational and commercial watercraft, for the most part, incorporate hulls which have V-shaped bottoms, with the V-shape, at its lowest point, forming a keel. The V-shape is thought to enable the boat, as speed is increased, to be pushed upwardly out of the water, as the water traversing against the boat's bow is forced sideways and downwardly at a vector to the outer shape of the hull. Such designs have worked well for years. The force of the water being pushed sideways and downwardly by the forward movement of the boat also provides a substantial stability to the boat, especially in turns and as the boat is steered into oncoming waves and the wakes from other boats.
One detriment to such hull designs is that the draft of the boat tends to be relatively deep in relation to the length and beam of the boat, thus requiring sufficient depth of water to accommodate that draft. Another detriment is that it requires a relatively large amount of force (and horsepower) to propel such a boat forward at a sufficient speed to stabilize the boat, i.e., to force the water sideways and downwardly as the boat travels generally horizontally through the water.
With V-shaped hull designs, initially, as velocity begins to increase from zero, the bow of the boat acts much like a plow, digging into and through the surface of the water. This creates what is known as a "bow wave". As velocity increases more, the bow tends to be forced upwardly by the sideways and downward force being applied to the water by the curvature of the V-shape of the hull being forced horizontally forward and up over the bow wave.
Finally, when sufficient velocity is approached then reached, the apex of the force on the V-shaped hull travel rearwardly along the hull, forcing the boat more upwardly to an increasing degree until a point is reached at which the bow, now out of the water, tends, by force of gravity, to descend toward the water, pivoting on the apex of the force against the sides and bottom of the V-shaped hull. This pivoting serves to raise the stern of the boat as the bow descends until the whole boat is lifted upwardly onto what is known as a plane. At this point, because there is relatively less water contacting the hull, drag from that water is reduced and the boat is correspondingly able to go significantly faster given the same amount of force propelling the boat forward.
Of course, as might be anticipated, the hydraulic force of the water against the V-shaped hull is substantial, thus an equally substantial counteracting force, provided by the engine of the boat, is required to get the boat up on a plane and to maintain it there. The ultimate speed of the boat, when up on a plane, depends on the specific design of the V-shaped hull, the weight (and weight distribution) of the boat, and the available power, i.e., the size of the engine and the size and pitch of the propeller which is driven by the engine. However, in all cases, the forward movement of the boat, at any speed, whether up on plane or not, is counteracted by both sideways and downward vectors of force produced by the relative hydraulic movement of the water against the hull.
The amount of fuel needed to power a boat at a given velocity is in direct proportion to the overall degree of forces needed to be overcome to move that boat forward over a given distance. The greater those forces, the greater will be the amount of fuel consumed. Thus as a general proposition, if fuel economy is a concern, hull designs are desirable which tend to reduce the overall amount of opposing forces directed against the hull during forward movement of the boat. One approach to this is the use of relatively flat bottom hulls wherein there is less counteracting hydraulic force imposed against the hull as the boat moves forward. A flat hull is more readily pushed directly up over the bow wave to a position substantially on top of the water, creating less displacement of water by the hull in the dynamic mode as distinguished from the static mode. In other words, dynamic displacement of water is significantly less with a flat bottom boat than with a V-shaped bottom. On the other hand, static displacement, when the boat is at rest, is substantially the same for a flat bottom or a V-bottom boat, given equivalent boat weights and hull surface contact with the water.
Watercraft or boats with flat bottom hulls have been known for years. Small fishing boats have been manufactured for years, the concept seemingly to produce a boat with a relatively shallow draft to enable sports fishermen to get into shallow waters along shorelines, into shallow, swampy areas, and into lakes, ponds and streams which are not sufficiently deep to accommodate the draft of conventional V-bottom boats. Some of these boats include hull designs which incorporate pontoons or sponsons for lateral stability and floatation, better enabling fishermen to stand near the sides of the boats without upsetting those boats.
Such designs have evolved into what are popularly called "bass boats". Bass boat hulls are relatively narrow, in relation to length, with generally flat bottoms and relatively shallow V-shapes, if any. The draft of these boats is relatively shallow in comparison to V-shaped hulls. Once up on a plane, the vector force of the water is mostly downwardly, forcing these boats to rise up out of the water to a greater degree at relatively slower speeds, thus ultimate velocity can be greater, and relatively less engine power may be required to reach a given velocity.
The down side is that, because bass boats are relatively narrow beamed and because there is relatively little sideways or lateral force being exerted against the hull of a bass boat, there is correspondingly less lateral stability, and, due to a relatively narrow beam, such boats tend to be more easily tipped over by laterally moving waves and the wakes of other boats. Also, such boats do not steer as easily or as precisely as those with distinct, V-shaped hulls, seemingly because bass boats incur relatively less opposing sideways forces, those forces which tend to hold a boat to a straight forward movement which can be precisely altered by a rudder device at the stern. Therefore, when steered to turn, bass boats tend to skid laterally sideways more readily, thus making turning a much less precise and controllable skidding action, rather than the positive, precisely controllable action of V-shaped hulls. Bass boat designs rarely incorporate sponsons, thus, for the sake of safety, it is almost necessary to slow some high-powered bass boats down, before turning, to both effect a more precise turn and to prevent the boat from flipping over.
Pontoon boats have, likewise, been known for years. The hull designs of conventional pontoon boats incorporate two, three, four or more pontoons, generally arranged such that each pontoon is generally parallel to each other and all run from bow to stern of the boat. A platform of some type or other is usually mounted horizontally to the tops of the pontoons to form a deck. Such boats also usually have a rather shallow draft in comparison to conventional V-bottom hull designs because they offer relatively greater static buoyancy due to a relatively significantly larger surface area of the hull being in contact with the water. On the other hand, pontoon boats are really deep displacement boats in that the contact of the pontoons with the water tends to displace a relatively greater volume of water in comparison to a V-bottomed boat of similar weight and size. The pontoons may be generally in the form of hollow cylindrical shapes with their ends shaped more or less to points. The bottoms of the pontoons may be round or they may be V-shaped over all or part of their lengths.
Pontoon boats are also quite cumbersome to maneuver, again, due to a greater degree of keel action in contact with the water (tending to keep the boat going in a straight line) and relatively greater counteracting hydraulic sideways force being exerted against the pontoons at any given velocity (again, also tending to keep the boat going in a straight line). Such boats are, consequently, normally used for relatively slow-speed cruising.
Racing boats, i.e., "hydroplanes", have for years incorporated sponson-like shaping along the sides to provide stability, due to increased width, with that portion of the bottom of the hull, which extends between and connects the sponsons, being raised above the lower level of the sponson bottoms. In such boats, the sponson-like shapes are usually modified such that they are somewhat V-shaped to form a keel at the lowest extending edges of each sponson. Thus, in effect, conventional hydroplanes will have two small V-shaped hulls, each extending at least part way from bow to stern of the boat at the lateral extremities. Water is channeled between these sponson hulls at a somewhat greater velocity than outboard of the hulls, generally following the jet principle. This relatively increased water flow velocity tends to work against the central flat bottom to raise the boat to a plane. Once the boat is up on a plane, the increased speed, with corresponding increased hydraulic force against the two hulls, tend to raise the flat central portion even more to a point where it is substantially above the general level of the water, thus further reducing hydraulic forces against the hull and enabling even greater speeds.
The problem is that once the central flat portion of the hull on a hydroplane is raised above the water level, there is relatively little hydraulic force imposed on the two sponson hulls to stabilize the boat, and almost none on the central flat bottom. A brisk wave, moderate chop or a stiff wake, suddenly imposed on the hull, tends to raise the whole boat out of the water and can easily flip the boat; at high speed, such a flip frequently proves to be fatal.
Water skis have also been known for years, and the sport of water skiing has grown into a sport that is engaged in by many people. Special ski boats have been designed to tow water skiers, although conventional outboard, inboard-outboard and inboard engine driven boats are also widely used for the sport of water skiing, provided they can reach sufficiently high speeds to enable the water skier, being towed behind, to get up erect (or semi-erect) and to induce his or her water skis to, more or less, plane on top of the water surface. To date, however, it appears that there has been no attempt to develop self-propelled water skis.